In downhole and drilling operations, it is often necessary to create an annular seal in the well in order to isolate one zone from another for such operations as installing casing and/or cementing zones of the well. For example, in the drilling of deep wells, it is often desirable to cement the casing in the wellbore in separate stages, beginning at the bottom of the well and working upwards. This process is achieved by placing cementing tools, which are primarily valved ports, in the casing or between joints of casing at one or more locations in the wellbore, flowing cement through the bottom of the casing, up the annulus to the lowest cementing tool, closing off or sealing the bottom, opening the cementing tool, and then flowing cement through the cementing tool up the annulus to the next upper stage and repeating the process until all stages of cementing the well are completed. The cementing tools often utilize sealing elements to create an annular seal between the tool and the wellbore or well casing prior to displacing cement into the well through the tool.
In another example, during the drilling and completing of oil wells, heavy steel casing is sometimes placed in a well and cement is placed between the casing and the well to anchor the casing in place and prevent migration of fluids outside the casing. After an upper portion of a well has been drilled and cased, it is common to continue drilling the well and to line a lower portion of the well with a liner lowered through the upper cased portion of the well. Liner hangers have been used to mechanically support the upper end of the liner from the lower end of the previously set casing and to seal the liner to the casing. Liner hangers have included slips for mechanical support and packers for forming a seal.
In both these applications and in others, elastomeric rings carried on a section of expandable tubing have been used to form the seal. When the seal is needed, an expansion cone can be forced through the tubing to expand the elastomeric rings into contact with the casing to provide both mechanical support and a fluid seal. One problem with the use of such systems is the amount of fluid pressure needed to drive the expansion cone through the expandable tubing. Often the fluid pressure has to be high enough that it can be problematic for other components of the tool, such as rupture disks, sometimes used to prevent premature entry of cement into well zones.